A Note on Marble Crayfish
1. Name
The common name is ‘Mystery Crayfish’ in Japan, derived from its mysterious unisexual reproduction. It is, however, called ‘Marble Crayfish’ overseas because of its marble pattern on the carapace.
It is sometimes called ‘Marmorkrebs’ that means ‘marble crayfish’ in German because this parthenogenesis crayfish was discovered in Germany.
The followings are just an aside, but Japanese should respect the globally generalized name though Japan has had tendency to create unique name for foreign crayfish. Even in China where everything is converted to Chinese character uses 大理石螯蝦 which means marble crayfish.
2. Discovery
Marble Crayfish was discovered to be parthenogenesis in 2003 by Dr. Gerhard Scholtz and his colleagues of Humboldt University Berlin, and reported in “Nature” magazine.
This became big news because parthenogenesis had not been previously reported in decapods, the largest crustacean, such as shrimp, crabs, crayfish and lobsters.
They described, “It has been rumored that an unidentified decapod crustacean, a crayfish of marbled appearance and of uncertain geographical origin that was introduced into the German aquarium trade in the mid-1990s, is capable of unisexual reproduction (parthenogenesis)”, and “here we confirm that this marbled crayfish ('Marmorkrebs') is parthenogenetic under laboratory conditions.”
Isn’t it pleasant that the important discovery came not from nature but from the artificial aquarium environment ?
Again an aside, but there seems to be an analogy between two discoveries - one from scientists who discovered parthenogenesis in 2003 whereas crayfish freaks had already known it since mid-1990s, and another from Columbus who discovered the new continent whereas the native American had been lived there since pre-history era.
3. Scientific Name
However, there are some skeptical voices against Procambarus fallax confirmation. Professor Keith Crandall, for example, of Brigham Young University says that it looks much more like a Procambarus alleni than a Procambarus fallax. He received tissue samples from Austrian and German Marble Crayfish keepers, sequenced these samples, compared them to his extensive database of crayfish and came to the conclusion of Procambarus alleni.
According to Dr. Scholtz, their morphological and molecular analysis showed that the Marble Crayfish belongs to the American Cambaridae family. And it was also identified as a Procambarus fallax. Indeed a Procambarus fallax has marble dots and therefore looks like ‘Marble Crayfish’.
But hold on! A Procambarus alleni is a Blue Florida Crayfish, isn’t it? The pattern on the carapace is marble, though the color is blue not brown, and looks like Marble Crayfish.
Which is true? Really confusing!
4. Self-Cloning Crayfish
Marble Crayfish is a self-cloning female crayfish and therefore offsprings are also clones of their mother. The places and shapes of dots on the carapace are the exactly same as those of a parent and sisters, though the color could vary according to the food.
Although parthenogenesis is wide spread among small and simple creatures like snail and water flea, it has never been seen among decapods, the largest crustacean, like crayfish. By virtue of its parthenogenetic reproduction, Marble Crayfish emerges not only as an interesting laboratory model but also as an economically important resource.
On the other hand, it is a potential threat in that it could outcompete native forms should even a single specimen be released into the natural environment. It is still not illegal to release this non-Special Alien Animal, but be sure not to release this creature into a river or a lake to avoid disastrous effect on the freshwater ecosystem.
Usually assignment is difficult prior to the scientific name specification, but we afraid that hasting MOE would assign both Procambarus fallax and Procambarus alleni from a preventive point of view, before the scientific name specification be completed. In that case, we will not be able to keep Blue Florida Crayfish anymore.
In near future the Ministry of Environment (MOE) might well assign Marble Crayfish to a Special Alien Animal that is prohibited not only to be released but also to be kept in a tank.
